Story County, Iowa: drinking water report. Story County in central Iowa has about 98,000 residents, including Ames and Iowa State University.
Story County in central Iowa has about 98,000 residents, including Ames and Iowa State University. The City of Ames draws from the Skunk River and a series of alluvial wells, while surrounding communities rely on groundwater from the glacial drift aquifer. Iowa's intensive row crop agriculture – corn and soybeans cover the vast majority of the county – defines the water quality challenges.
Nitrate is the primary concern. Ames Water Treatment Plant regularly processes raw water with nitrate concentrations above the MCL of 10 mg/L during spring, requiring blending with lower-nitrate sources or ion exchange treatment. According to the Iowa DNR's 2024 drinking water compliance data, the Ames system's raw water nitrate peaked at 14.2 mg/L in May 2024 following heavy spring rains that flushed fertilizer from surrounding fields.
Atrazine follows a similar seasonal pattern, with spring flush concentrations occasionally approaching the MCL of 3 ppb. A 2024 Iowa Geological Survey study found that 30% of private wells in Story County's glacial drift showed nitrate above 5 mg/L, indicating widespread agricultural contamination of the shallow aquifer.
Iowa's agricultural intensity means nitrate is not a hypothetical concern – it is a seasonal operational challenge that Ames Water actively manages. The treatment plant handles it, but private well owners outside the municipal system do not have that protection.
Check your water for current data. For nitrate, reverse osmosis is the most reliable household solution. Our water filter guide ranks systems by certified nitrate removal. Pull your detailed report for seasonal patterns, and visit our Iowa page for statewide context.